[testing] Update README.md

[emmyoop]

Resolves #

Problem

Solution

Checklist

• I have read the contributing guide and understand what's expected of me.
• I have run this code in development, and it appears to resolve the stated issue.
• This PR includes tests, or tests are not required or relevant for this PR.
• This PR has no interface changes (e.g., macros, CLI, logs, JSON artifacts, config files, adapter interface, etc.) or this PR has already received feedback and approval from Product or DX.
• This PR includes type annotations for new and modified functions.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.42%. Comparing base (984005a) to head (21ab861).
⚠️ Report is 33 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #12715   +/-   ##
=======================================
  Coverage   91.42%   91.42%           
=======================================
  Files         203      203           
  Lines       25803    25803           
=======================================
  Hits        23591    23591           
  Misses       2212     2212           

Flag	Coverage Δ
integration	88.30% <ø> (-0.02%)	⬇️
unit	65.50% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
Unit Tests	65.50% <ø> (ø)
Integration Tests	88.30% <ø> (-0.02%)	⬇️

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.